There are already numerous processes for producing high molecular weight crosslinked and uncrosslinked diisocyanate polyaddition products of average and high molecular weight which are soluble in organic solvents. In these processes, water, glycols, diamines, hydrazines, hydrazine hydrate, hydrazine derivatives or carbodihydrazide, for example, are used as chain extenders and crosslinkers (German Auslegeschrift Nos. 1048408, 1183196 and 1184984, German Offenlegungsschrift No. 2015603 or U.S. Pat. Nos. 3248424, 3184426 or 3399167).
In conventional isocyanate polyaddition processes, it is often difficult to synthesize high molecular weight polyaddition compounds with a high content of urethane and, more especially, urea or hydrazodicarbonamide groups because, on account of their isocyanate-reactive hydrogen atoms, these groups actually lead, during the polyaddition reaction, to undesirable branching especially in the production of solutions with high solids content. However, since solubility and thermoplastic processibility of the polyaddition compounds are governed to a considerable extent by the linear structure of the macromolecule, the production of soluble, thermoplastically processible isocyanate polyaddition products has hitherto been confined to relatively narrow ranges of urethane and, more especially, urea or hydrazodicarbonamide contents. For example, experience has shown that the production, from difunctional NCO-prepolymers and water or diamines as chain extenders, of soluble polyurethane polyureas, which are storable in solution form and do not show any tendency towards gelation, is particularly difficult when the content of chain-extending urea groups --NH--CO--NH-- exceeds a level of 5.2% by weight. In this case, and especially when the NCO-prepolymer are chain-extended in an NCO:NH.sub.2 ratio of 0.9 to 1.2, it is only possible to obtain readily gelling solutions of limited shelf life in which from 10 to 20% by weight of gel fractions may be detected by centrifuging. These gel fractions are insoluble, for example, even in strongly polar solvents, such as dimethylformamide or dimethylacetamide, and may only be dissolved over prolonged periods at elevated temperatures, accompanied by the heat-induced breakup of crosslink sites. If the concentration of the ##STR2## units in the solid product is increased to between 8 and 10% by weight or more, completely insoluble polyaddition products are obtained because, on the one hand, the urea groups are able to react to form biuret branchings and crosslinks and because, on the other hand, the concentrations of urea segments capable of forming strong hydrogen bridge bonds is so high that reversible gels begin to form at room temperature. The products in question are branched polyaddition products which only dissolve under the action of heat, generally at temperatures in the range of from 50.degree. to 70.degree. C. Even when optimum manufacturing techniques are applied, for example, gradual introduction of the NCO-prepolymers at low temperatures into dilute solutions of the chain extenders, apparently stable solutions often gel after only a short time. Their dispersion or dissolution involves considerable difficulties so that it is not possible to produce, for example, elastomeric lacquer coatings, sheet structures and coatings on wood, metal, fabric or leather substrates, plastics-based lacquer finishes and coatings. High urea group concentrations in the polyaddition products coupled with high solids contents of, for example, from about 30 to 50% and with high molecular weights (NCO-NH.sub.2 ratio= 1) have in the past always resulted in the formation of reversibly gelling or crosslinked, irreversible gels, even where dimethylformamide is used as solvent.
It has now surprisingly been found that extremely high molecular weight, readily soluble,
linear and, hence, also thermoplastically processible or film forming (from solutions of high solids concentration), PA1 polyurethane ureas, polyureas, polyurethane-polyurea-polyhydrazodicarbonamides or polyurethane-polyhydrazodicarbonamides with optionally very high urea and/or hydrazodicarbonamide concentrations, may be obtained in a smooth, reproducible reaction providing the urea segments of the polyaddition products are partially or completely substituted by organic phosphonic acid ester radicals. PA1 R.sub.1 and R.sub.2 are the same or different and represent hydrogen or a C.sub.1 -C.sub.18 alkyl radical, C.sub.4 - C.sub.10 cycloalkyl radical or a C.sub.6 -C.sub.10 aryl radical, PA1 R.sub.3 and R.sub.4 are the same or different and represent hydrogen, a C.sub.1 -C.sub.18 alkyl radical, C.sub.4 -C.sub.10 cycloalkyl radical, C.sub.6 -C.sub.10 aryl radical, in addition to which PA1 R.sub.1 and R.sub.2 or R.sub.3 and R.sub.4 together with the carbon atoms between nitrogen and phosphorus can form a 5 to 7 membered isocyclic ring, and PA1 R.sub.5 represents a C.sub.1 -C.sub.4 alkyl, cyclohexyl or phenyl radical. PA1 R.sub.1, r.sub.2, r.sub.3 and R.sub.4 are the same or different and represent hydrogen, a C.sub.1 -C.sub.18 alkyl radical, C.sub.4 -C.sub.10 cycloalkyl radical, C.sub.6 -C.sub.10 aryl radical, in addition to which PA1 R.sub.1 and R.sub.2 or R.sub.3 and R.sub.4, together with the carbon atom between the nitrogen and phosphorus, may form a 5-- to 7-- membered isocyclic ring; PA1 R.sub.1, r.sub.2, r.sub.3, and R.sub.4 and preferably represent hydrogen, an aliphatic hydrocarbon radical with 1 to 4 carbon atoms or an aromatic hydrocarbon radical with 6 to 10 carbon atoms. Compounds of formulae (A) and (B), in which R.sub.1 and R.sub.2 or R.sub.3 and R.sub.4 together with the carbon atom between nitrogn and phosphorus, can form a 5-- to 7-isocyclic ring, are also preferred. PA1 R.sub.5 represents a C.sub.1 -C.sub.4 alkyl radical, a cyclohexyl radical or even a phenyl radical. R.sub.5 preferably represents an aliphatic C.sub.1 -C.sub.4 hydrocarbon radical. PA1 Q' represents preferably a hydrocarbon radical such as a divalent C.sub.2 -C.sub.18 alkyl radical, C.sub.4 -C.sub.13 cycloalkyl radical, C.sub.7 -C.sub.11 aralkyl radical or C.sub.6 -C.sub.14 aryl radical optionally interrupted by oxygen, sulphur or nitrogen and optionally substituted by a C.sub.1 -C.sub.8 alkyl radical, N(R.sub.6) [R.sub.6 = C.sub.1 -C.sub.8 alkyl radical, C.sub.4 -C.sub.10 cycloalkyl radical, C.sub.7 -C.sub.11 aralkyl radical], nitro and/or halogen atoms. Q' preferably represents an aliphatic C.sub.2 -C.sub.8 hydrocarbon radical, a cycloaliphatic C.sub.6 -C.sub.13 hydrocarbon radical, an araliphatic C.sub.7 -C.sub.8 hydrocarbon radical or an aromatic C.sub.6 -C.sub.14 hydrocarbon radical. PA1 Q quite generally represents the radical obtained by removing the isocyanate groups from an organic diisocyanate with a molecular weight in the range of from 140 to 6000. Q preferably represents an aliphatic C.sub.4 -C.sub.12 hydrocarbon radical, a cycloaliphatic C.sub.4 -C.sub.15 hydrocarbon radical, an aromatic C.sub.6 -C.sub.15 hydrocarbon radical or an araliphatic C.sub.7 -C.sub.8 hydrocarbon radical.